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RIPARIAN VEGETATION <br />The importance of riparian vegetation for <br />influencing channel stability and form, bank <br />characteristics, floodplain processes and others <br />is becoming increasingly recognized. Similarly, <br />a shift in hydrologic regime that decreases the <br />frequency and magnitude of peak flows can <br />have a major effect on the composition and <br />characteristics of riparian plant communities. <br />Changes in hydroperiod (i.e., the length of <br />time that riparian soils are saturated) due to <br />dam operations or stream diversions may have <br />important implications for the establishment, <br />growth, and succession of riparian dependent <br />plant species. <br />Although suppression of peak flows may <br />provide improved bank stability, the loss of <br />incremental channel changes during high flows <br />may potentially eliminate plant species that are <br />dependent upon high flows. For example, <br />gallery forests of cottonwoods along many <br />western streams may be slowly eliminated <br />where peak flows have been suppressed or <br />channels have been structurally stabilized. <br />The ability of streamside vegetation to <br />influence water quality and channel processes <br />is highly varied. It may include, for example, <br />stream shading by overstory canopies (thus <br />affecting stream temperatures), seasonal leaf <br />and litter inputs (a source of biotic energy for <br />many instream invertebrates and other aquatic <br />species), bank stability associated with the <br />occurrence of root systems (particularly woody <br />root systems), improved fish habitat from the <br />recruitment of large woody debris, altered <br />nutrient cycling, increased channel roughness <br />during overbank flows from above- ground <br />portions of plants (i.e., stems and leaves), and <br />others. Many of these changes are closely <br />associated with a variety of recreational values <br />(campsite quality, aesthetics, etc.), and it is also <br />important to consider the long -term <br />implications of altered flows on the ecological <br />integrity and characteristics of riparian plant <br />communities. <br />play a critical role in determining the type and abundance of vegetation, which <br />in turn can affect other resources. <br />28 <br />